The fuel supply system of a jet engine (turbofan engine) that is used for an airplane and the like generally has a constitution that boosts pressure of fuel from the fuel tank by means of a fuel pump that is a booster portion, determines the flow rate by means of a fuel metering mechanism, sends that fuel to the engine combustor in the jet engine, and returns the surplus fuel to an inlet of the fuel pump.
A gear pump has conventionally been used as the fuel pump. Rotational movement that is transmitted from the engine drives the gear pump via gears in an accessory gear box serving as an engine auxiliary device. For this reason, the amount of discharge of the gear pump is approximately proportional to the rotational frequency of the engine.
With such a gear pump, it is possible to boost the fuel pressure by confining the fuel to a closed space that is formed by the gears and the inner wall surface of the casing.
In recent years, a double gear pump as disclosed for example in Patent Document 1 has been employed. A double gear pump is equipped with two driven gears that are oppositely arranged with the drive gear therebetween, and so boosts the fuel pressure by confining the fuel to a closed space that is formed by the two driven gears and the casing. For this reason, it is possible to obtain a sufficient discharge amount even in the state of low-speed rotation of the drive gear.
[Patent Document 1] Japanese Unexamined Patent Application, first publication No. 2003-328958